Hans Mommsen was a leading exponent of the ‘functionalist’ interpretation of the Nazi era.
Photograph: Photoshot

The historian Hans Mommsen, who has died aged 85, persuaded Germans to rethink the catastrophe of nazism. He forcefully rejected what he saw as not just simplistic but inherently apologetic attempts to reduce responsibility for Germany’s disaster to the ideology, intentions and actions of Hitler and his immediate underlings.

He never wavered in his vehement opposition to what he saw as Hitler-centric approaches to the Nazi past. Down to the end of the 1970s, these – which collectively came to be known as the “intentionalist” school – had amounted to orthodoxy among leading German experts on the Third Reich. Mommsen’s interpretation – labelled the “functionalist” approach – instead turned the focus on to the actual practice of the regime.

This transferred responsibility to wide sections of German society, principally to the national conservative elites – business leaders, the aristocracy, the higher civil service, the judiciary, above all the military leadership – both for their role in allowing Hitler to take power and subsequently for their extensive collaboration with the Nazi regime.

Mommsen analysed precisely how Nazi rule undermined and eroded the formal structures of government, prompting a process of “cumulative radicalisation”, which ended in the regime “running amok” in a maelstrom of destruction and criminality.

He first stirred bitter debate in the early 1960s with a highly influential article about the Reichstag fire of 1933. Until then it had been largely presumed that the Nazis had themselves set fire to the Reichstag as part of a preconceived design to take over the German state. Mommsen argued, however, that a young Dutch communist, Marinus van der Lubbe, had acted alone. Hitler and other leading Nazis, he claimed, had merely exploited the opportunity provided by the fire to cement their hold on power.

Conservative historians in West Germany responded with fury to what they saw as a trivialisation of Hitler’s plan to gain totalitarian power. Undeterred, Mommsen, in his Beamtentum im Dritten Reich (The Civil Service in the Third Reich, 1966), provocatively asserted that Hitler was in some respects a “weak dictator” – essentially a propagandist preoccupied with upholding his own standing, an indecisive leader who stood under the influence of his entourage.

When he turned to explain the implementation of the Final Solution, Mommsen’s approach inexorably led to further controversy, prompted by his essay Die Realisierung des Utopischen (1983, later published in English translation as The Realisation of the Unthinkable). Mommsen accepted that Hitler’s relentless anti-Jewish rhetoric had done much to stimulate the climate that produced the exterminatory policy, but ruled out any specific order, looking instead to the inner dynamics of a system running increasingly out of control. His interpretation was later more fully expounded in his book Das NS-Regime und die Auslöschung des Judentums in Europa (The Nazi Regime and the Annihilation of the Jews in Europe, revised version 2014).

Mommsen also wrote extensively on German resistance to Nazi rule. As far back as the 1960s, he was strongly critical of the way in which the political culture of the Federal Republic had turned conservative opponents of Hitler – notably the army officers and higher civil servants who conspired to kill Hitler in 1944 – into iconic forerunners of postwar democracy. He showed instead the continuity of their authoritarian ideas and their antisemitism from the 1920s onwards, and how, in a lengthy process, growing disillusionment had gradually led a courageous minority to try to overthrow the regime. It amounted to a substantial revision of the roots of conservative resistance.

His personal experience of the chaos, destruction and gross inhumanity during the last months of Nazi rule helped to shape Mommsen’s passionate commitment to widening a public understanding of how Germany could have produced such a collapse of civilisation. Such an understanding was for him an essential basis for the consolidation of German democratic structures and values. It followed that, when the bitter “Historians’ Dispute” (Historikerstreit) exploded in 1986 around the question of the uniqueness of the Holocaust, Mommsen found himself at the forefront of attacks on conservative historians who in his view were dangerously relativising German responsibility for the murder of the Jews by suggesting that Stalin’s crimes were worse.

Born in Marburg, north of Frankfurt, Hans was the son of Marie-Therèse (nee Iken) and Wilhelm Mommsen. His father was professor of modern history at Marburg and, indeed, the Mommsens formed a virtual dynasty of historians. Hans’s great-grandfather, the ancient historian Theodor Mommsen, had been awarded the Nobel prize for literature, and Hans’s twin brother, Wolfgang, who died in 2004, went on to become an eminent historian of imperial Germany.

Hans studied history, German and political science in Marburg and Tübingen, gaining his doctorate in 1959, before teaching in Heidelberg from 1963 to 1968. He was then appointed to the chair of modern history in the new Ruhr University at Bochum, where he remained until his retirement in 1996. He was well known outside Germany and held visiting professorships at Harvard, Princeton, Berkeley, Jerusalem and Oxford. Notable among a number of awards was the 2010 Bruno Kreisky prize in Austria for his lifetime’s work.

His book Die Verspielte Freiheit (1989) appeared in English translation in 1996 as The Rise and Fall of Weimar Democracy. Some of his many brilliant essays were brought together in English translation in From Weimar to Auschwitz (1991) and Alternatives to Hitler: German Resistance under the Third Reich (2003).

In his later years, however, Mommsen’s interpretation of the Third Reich came under fire from a new generation of historians. In his concentration on abstract processes and structures, they argued, Mommsen had left human agency – that of the perpetrators of nazism’s dire crimes against humanity – largely out of the picture, and had gravely underestimated the importance of ideology. There was force in both objections. Mommsen’s stubborn insistence on his own interpretation meant that he felt a sense of alienation as he was squeezed to the fringes of mainstream research.

He was often aggressive and confrontational towards his fellow historians, though invariably warm and encouraging in his dealings with younger colleagues. He was also enormously supportive of his students, and I was struck, when deputising for him at Bochum in 1983-84 while he was on research leave, by the depth of their affection for him.

In 1966 he married Margareta Reindl, now professor emerita of political science at Munich University and an expert on Putin’s Russia; she survives him.